Speaker
Johannes Thomas Gebhard
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O4.201.pdf
Coherent proton acceleration from isolated micro-plasmas
J. Gebhard1 , T.M. Ostermayr1,2 , D. Haffa1 , E. Sperling1 , P. Hilz1 ,
J. Schreiber1,2
1 Ludwig-Maximilians-Universität,Am Coulombwall 1,85748 Garching, Germany
2 Max-Planck-Institut für Quantenoptik, Hans-Kopfermannstr 1, 85748 Garching, Germany
We present a unique target system to position micrometer sized targets freely levitating in
the focus of a PW laser. The system is based on an electrodynamic trap [1], enabling the use of
targets of different form and material. First experiments at the Texas-PW laser [2] allowed for
studying the transition from Coulomb explosion towards plasma expansion for increasing target
diameters. Experiments at the PHELIX PW laser resulted in a coherent proton acceleration with
a narrow energy spectrum around 30 MeV [3]. The novel acceleration mechanism is based on a
plasma density slightly below the critical density and features a very good reproducibilty. The
density is reduced due to pre-expansion in the rising edge of the laser pulse, which at the same
time limits the acceleration process that stops long before the main pulse arrival. As a result
only a small fraction of the overall laser energy is effectively used for particle acceleration.
Future experimental plans are targeted to shape a fs laser pulse to control the plasma con-
ditions at the main pulse and thus increase the conversion efficiency from laser into particle
energy. We plan plasma expansion studies of isolated micro-plasmas at intensities up to 1018
W/cm2 using the ZEUS laser, which also has a separate probe beam path, at the ’Centre for Ad-
vanced Laser Applications’ (CALA) in Garching. In this scope we are currently atomizing the
operation of the target positioning system for a faster trapping process and (sub-minute) target
replacement. This is also a necessary requirement for future experiments at higher repetition
rate of the 3 PW ATLAS 3000 laser.
References
1. T. M. Ostermayr et al., Review of Scientific Instruments 89, 013302 (2018).
2. T. M. Ostermayr et al., Phys. Rev. E 94, 033208 (2016).
3. P. Hilz et al., Nature Communications 9, 423 (2018).
